Dual cam pulse timer switch

ABSTRACT

A cam-actuated timer switch utilizes two cams substantially rotating together, but having a small predetermined degree of angular freedom in relation to each other, to produce periods of electrical switch substantially short in duration.

United States Patent 1191 Voland et al. June 18, 1974 [5 DUAL CAM PULSE TIMER SWITCH 3,627,937 12/1971 Swanke et a1 zoo/3s B Inventors: m W. voland napol s; 3,742,160 6/1973 Murray et al 200/38 BA X Kenneth E. Deane, Beech Grove, both of Primary Examiner.lames R. Scott [73] Assignee: P. R. Mallory & Co., Inc., Attorney, Agent, or Firm-Richard H. Childress;

Indianapolis, Ind. Charles W. Hoffmann; Robert F. Meyer [22] Filed: Mar. 26, 1973 [21] Appl. No.: 345,130

[57] ABSTRACT [52] US. Cl 200/38 B, 200/38 BA, 200/153 LB [51] Int. Cl. H0lh 43/10 A cam-actuated timer switch utilizes two cams sub- [58] Field of Search 200/38, 153 L, 153 LA, Stantially rotating together, but having a small prede- 200/153LB termined degree of angular freedom in relation to 2 each other, to produce periods of electrical switch [56] References Cited substantially short in duration.

UNITED STATES PATENTS 3,581,028 5/1971 Valbona 200/38 R 4 Claims, 4 Drawing Figures 1 DUAL CAM PULSE TIMER SWITCH Generally speaking, the present invention relates to a cam-actuated timer switch including mounting means, a shaft rotatably journaled in the mounting means, drive means for imparting a constant speed rotation to the shaft, at least one cam pair comprising a One application of this kind of timer switch is in a domestic automatic clothes dryer. With the advent of permanent press clothes has come the need on' the part of dryer manufacturers for a timer that can produce very short pulses of time-controlled switching. These pulses are used to periodically switch on the drum motor of a dryer to rotate the drum a few revolutions during the cool-down period so that the clothes will have less wrinkles than if they were allowed to sit in one position while cooling down. The ordinary dryer timer, because of its slow cam movement and lifter construction, cannot produce these short pulses. The pulses can and are being achieved by the addition of a separate high speed timer or by a more expensive switching apparatus added to the ordinary timer. The resulting additional expenses result in a wrinkle eliminating feature appearing only on the more expensive top-of-the-line dryers. In the application example previously stated, the present invention utilizes the same inexpensive switching components as are used in a simple dryer timer and requires the addition of only one part an inexpensive secondary cam.

Accordingly, a feature of the present invention is to provide a cam-actuated timer switch featuring a means for producing short pulses of time-controlled switching. Another feature of the present invention is to provide a neat, compact and economical cam-actuated timer switch featuring a means for producing short pulses of time-controlled switching. Still another feature of the present invention is to provide a camactuated timer switch wherein a pair of cams cooperate with one switching member toproduce short pulses of timecontrolled switching. A further feature of the present invention is to provide a cam-actuated timer switch including a V-shaped cam follower responsiveto counter-clockwise and clockwise rotation of a cam pair. Yet another feature of the present invention is to provide a cam-actuated timer switch including a keying means for coupling two cams together. Still another feature of the present invention is to provide a cam-actuated timer switch wherein a cam pair includes a first cam keyed to a shaft and a second cam keyed to the first cam. A further feature of the present invention is to provide a cam-actuated timer switch including a limit means to provide a controlled degree of rotational free dom of one cam to another cam.

These and other features of the invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view illustrating the embodiment of the invention as it relates to an automatic clothes dryer timer switch.

FIG. 2 is a front elevation of the embodiment shown in FIG. 1.

FIG. 3 is the same view of the embodiment as shown in FIG. 2 but with the cams of the timer switch in a different position.

FIG. 4 is an exploded view of the primary and secondary cams of the timer switch.

Referring now to the drawings which illustrate the preferred embodiment of the present invention, a drive means 10 is carried on a mounting means 12 by an attachment means 14. Drive means 10 comprises a permanent magnet synchronous gear motor 16. Mounting means 12 comprises a housing 18. Attachment means 14 includes screws 20 which are threaded into holes 22 in housing 18. An output shaft 17 extends from a synchronous gear motor 16. A pinion 19 carried on the output shaft 17 engages a gear 21 carried on a shaft 24. Shaft 24 is journaled for rotation in housing 18.

Keying means 26 comprises two flat surfaces 28 provided on shaft 24 and a mating hole 30 in a primary cam 32. The hole 30 is located substantially in the center of the primary cam' 32 and shaped to key onto the double flat portion 28 of shaft 24. Also keyed to the shaft 24 is a cam stack 25 which, in the case of a clothes dryer'timer, provides a program for the normal operation of the clothes dryer.

A secondary cam 38 is journaled to loosely rotate about the shaft 24. The degree of rotational freedom of the secondary cam 38 about the shaft in respect to primary cam 32 is controlled by a limit means 40. Limit means 40 includes two projections 41 molded as part of primary cam 32. These two projections fit into slots 42 in secondary cam 38 to key the secondary cam to the primary cam 32.

A cam profile 44 corresponding to a program for the timer is provided on the periphery of each of primary cam 32 and secondary cam 38. Cam profile 44 includes a plurality of high radius arcuate surfaces 43 and low radius arcuate surfaces 45 wherein surfaces 43 drop abruptly to surfaces 45 and surfaces 45 rise to high radius surfaces 43 in accordance with a program of the timer.

A plurality of primary cam pulse lobes 46 comprises a portion of the cam profile 44. Corresponding to these pulse lobes are secondary cam pulse lobes 48 on secondary cam 38 which are of the same angular size and spacing as the primary cam pulse lobes 46. In FIGS. 2 and 3 the direction of rotation of the shaft 24 is clockwise. The degree of angular freedom between primary cam 32 and secondary cam 38, allowed by projections 41 in the slots 42, is such that the lobes 46 and 48 align together in one extreme limit of the freedom as shown in FIG. 2. And, at the other limit of freedom as shown in FIG. 3, the secondary cam 38 is displaced an angle equal to about one half the angle occupied by the space between lobes 46 and 48 in a counter-clockwise direction from the position in which the lobes align.

Electrical switching means 36 is coupled to housing 18 by connection means 34. Connection means 34 comprises terminals 50 and terminal slots 52. Electrical switching means 36 includes a contact-carrying blade 54 and a fixed electrical contact 59 spaced from an electrical contact 58 disposed on said contact carrying blade. Contact-carrying blade 54 comprises a flexible metal blade 51 with bladecontact 58 affixed to it and a V-shaped follower 60 provided on the metal blade 57. Blade contact 58' makes and breaks electrical contact with fixed contact 59 in response to the program on primary cam 32 and secondary cam 38. Follower 60 includes a trailing sloped tip 62 and a leading sloped tip 64. Follower 60 engages both primary cam 32 and secondary cam 38. u

The tops of lobes 48 on secondary cam 38 are slightly greater in radius than are lobes 46 of primary cam 32 so that follower 60 touches only secondary cam 38 when the top of the two lobes 46 and 48 coincide under the follower. T

In operation, drive means causes shaft 24 to rotate slowly at a constant speed. Primary cam 32 being keyed to the shaft 24 is rotated at the same speed. Secondary cam 38, being keyed to primary cam 32 through projections 41 and slots 42, rotates with primary cam 32 also at the speed of shaft 24. As the lobes 46 and 48 pass under follower 60, the drag'of the follower on the slightly higher cam radius of secondary cam 38 tends to retard the secondary cam to one limit of its angular freedom in respect to primary cam 32. FIG. 3 shows the relationship of primary and secondary cams 32 and 38 to follower 60 for this condition.

As the cams 32 and 38 continue to rotate clockwise from the position shown in FIG. 3, follower 60 drops off a lobe 48 of secondary cam 38. The trailing sloped side 62 of the follower 60 flips lobe 48 in the clockwise direction as the follower drops. lmmediately after follower 60 has dropped, the leading sloped side 64 is in a position in a space between lobes to be picked up almost immediately by a lobe 46 on primary cam 32. Upon the dropping of the follower, blade contact 58 engages fixed contact 56 and starts an electric pulse. The pulse lasts a relatively short time. Lobe 46 on primary cam 32 engages and lifts follower 60 shortly after it drops off a lobe 48 of secondary cam 38, whereupon the contacts 58 and 59 disengage and terminate the electric pulse. These short periodic electric pulses switch on the drum motor of a dryer to rotate the drum a-few revolutions during the cool-down period.

What is claimed is:

l. A cam-actuated timer switch comprising:

a. mounting means;

b. a shaft rotatably journaled in said mounting means;

c. drive means carried by said mounting means and coupled to said shaft for imparting a constant speed rotation thereto;

d. at leastone cam pair comprising a primary cam carried by said shaft and a secondary cam carried by said primary cam, each of said primary and secondary cams including a cam profile comprising a plurality of high radius and low radius arcuate surfaces, said high radius surfaces dropping off abruptly tolow radius surfaces and said low radius surfaces rising to said high radius surfaces, said drop-offs and rises being angularly spaced in accordance with a program of said timerwherein said high radius surfaces of said secondary cam are of slightly greater radii than said high radius surfaces of said primary cam;

e. limit means for keying said secondary cam to said primary cam to provide a controlled degree of rotational freedom of said secondary cam in relation to said primary cam;

f. keying means for keying said primary cam to said shaft; and

g. electrical switching means connected to said mounting means including a V-shaped cam follower carried on a contact-carrying blade and engaging said high and low radius arcuate surfaces of v said cam pair, whereby said V-shape follower is responsive to a timer program defined by said high and low radius arcuate surfaces.

2. A cam-actuated timer switch according to claim 1 wherein said shaft includes at least one flat surface and said primary cam includes amating shape to the portion of said shaft having said flat surface, whereby said primary cam is keyed to said shaft.

3. A cam-actuated timer switch according to claim 1 wherein said drive means comprises a permanent magnet synchronous gear motor.

4. A cam-actuated timer switch according to claim 1 wherein said limit means comprises at least one projection disposed on said primary cam engaging at least one slot on said secondary cam providing a predetermined amount of angular play between said primary cam and said secondary cam. 

1. A cam-actuated timer switch comprising: a. mounting means; b. a shaft rotatably journaled in said mounting means; c. drive means carried by said mounting means and coupled to said shaft for imparting a constant speed rotation thereto; d. at least one cam pair comprising a primary cam carried by said shaft and a secondary cam carried by said primary cam, each of said primary and secondary cams including a cam profile comprising a plurality of high radius and low radius arcuate surfaces, said high radius surfaces dropping off abruptly to low radius surfaces and said low radius surfaces rising to said high radius surfaces, said drop-offs and rises being angularly spaced in accordance with a program of said timer wherein said high radius surfaces of said secondary cam are of slightly greater radii than said high radius surfaces of said primary cam; e. limit means for keying said secondary cam to said primary cam to provide a controlled degree of rotational freedom of said secondary cam in relation to said primary cam; f. keying means for keying said primary cam to said shaft; and g. electrical switching means connected to said mounting means including a ''''V''''-shaped cam follower carried on a contactcarrying blade and engaging said high and low radius arcuate surfaces of said cam pair, whereby said ''''V''''-shape follower is responsive to a timer program defined by said high and low radius arcuate surfaces.
 2. A cam-actuated timer switch according to claim 1 wherein said shaft includes at least one flat surface and said primary cam includes a mating shape to the portion of said shaft having said flat surface, whereby said primary cam is keyed to said shaft.
 3. A cam-actuated timer switch according to claim 1 wherein said drive means comprises a permanent magnet synchronous gear motor.
 4. A cam-actuated timer switch according to claim 1 wherein said limit means comprises at least one projection disposed on said primary cam engaging at least one slot on said secondary cam providing a predetermined amount of angular play between said primary cam and said secondary cam. 